There is no reason to medicate new fish; better to put in the quarantine and monitor, and treat if a parasite develops. Many times the fish never get sick in quarantine, so there is no need to introduce a stressor (such as an anti-parasitic or antibiotic) to a healthy fish.

It is, of course, always good to have the basic meds on hand, just in case they are required for a fish that does get sick; make sure to always check expirations dates as meds do expire on a regular basis.

There are some who argue a low dose of Copper, but I worked for an aquarium for eight years and we never employed this practice, as we felt it introduced unnecessary stress, for both saltwater and freshwater species.

And fish always have ich on their body; it only becomes prevalent when conditions deteriorate or immune systems are compromised.

One of THE most important things in a quarantine is clean, clean water; utilizing a larger filter will always be better for the long term, and frequent water changes (especially after removing a fish batch following a quarantine cycle).